Effective Memory Management - Memory Hygiene

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Effective Memory Management - Memory Hygiene

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Perfectionism?

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Performance GoalsNameTarget (ms)Upper Bound (ms)UX / FeedbackInstant50010000Long, show Progress Dialog w/CancelExtended>500>10000Long enough for the user to switch to something else

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premature optimization is the root of all evil- Donald E. Knuth, Structured Programming with go to Statements

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-Performance is a feature?-No!

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Any memory issues?

usingSystem; namespaceConsoleApplication1 { internalclassProgram { privatestaticvoidMain(string[]args) { Console.WriteLine("ThisOShas{0}objectgenerations.",(GC.MaxGeneration+1)); varmyClass=newMyClass("First",100); Console.WriteLine("\nGenerationofmyClassis:{0}",GC.GetGeneration(myClass)); varamount=50000000; vartonsOfObjects=newobject[amount]; for(vari=0;i= 85,000 bytes) gen3

usingSystem; usingSystem.IO; namespaceConsoleApplication1 { classProgram { staticvoidMain(string[]args) { varcandidateToLargeObjectHeap=newlong[85000/8]; varmaxGen=GC.MaxGeneration; varobjectGen=GC.GetGeneration(candidateToLargeObjectHeap); Console.WriteLine($"ObjectSize:{GetObjectSize(candidateToLargeObjectHeap)}"); Console.WriteLine($"{nameof(maxGen)}:{maxGen}"); Console.WriteLine($"{nameof(objectGen)}:{objectGen}"); } privatestaticintGetObjectSize(objecttestObject) { varbf=newSystem.Runtime.Serialization.Formatters.Binary.BinaryFormatter(); using(varms=newMemoryStream()) { bf.Serialize(ms,testObject); returnms.ToArray().Length; } } } } 13

Collector

Stop the world!

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What happens during a collection

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Stop collecting during critical code pathsWithin .NET 4.6GC.TryStartNoGCRegionGC.EndNoGCRegion

Before .NET 4.6GCSettings.LatencyMode = LowLatency

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Garbage Collection NotificationsGC.WaitForFullGCApproachif (GC.WaitForFullGCApproach() == GCNotificationStatus.Succeeded) // Method that tells the queuing server to not direct requests to this server.

GC.WaitForFullGCCompleteif (GC.WaitForFullGCComplete() == GCNotificationStatus.Succeeded)// Informs the queuing system that this server is ready to accept requests again.

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Workstation GC with concurrent GC on

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Server GC with concurrent GC off

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Server GC with concurrent GC on

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Configure different GC modes Element

Element

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Efficiency is not where collect, but where do not allocateAllocation is the root of all evil

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Strings

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Strings | String.FormatcommonOptimal

int i = 5;String.Format("i = {0}", i);24

Strings | String Interpolation (C#6.0)commonOptimal

int i = 5;var formatted = $"i = {i}";25

Closure

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Closure | SimpleSource

Compiler-generated code

usingSystem; namespaceConsoleApplication1 { classProgram { staticvoidMain(string[]args) { intcount=0; Actionaction=()=> { count++; }; action(); } } }27

Closure | ComplexSourceCompiler-generated code

usingSystem; usingFluentTasks; namespaceConsoleApplication1 { classProgram { staticvoidMain(string[]args) { vartasks=newFluentTask(); varstring1="toBeCaptured1"; varstring2="toBeCaptured2"; tasks.AddTask(()=> { vartemp=string1+"somecoolinformation"; }, ()=>{vartemp=string2+"somegreatinformation";}); } } } namespaceFluentTasks { publicclassFluentTask { Action_taskAction; Action_onComplete; publicFluentTaskAddTask(ActiontaskAction,ActiononComplete) { _taskAction=taskAction; _onComplete=onComplete; returnthis; } } }28

IList vs List

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IList vs ListIlist (referencesource)List (referencesource)

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Create empty collectionCommon referencesource Optimal referencesource

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Resizing CollectionsDictionary.ResizeList.SetCapacity

usingSystem; usingSystem.Collections.Generic; namespaceConsoleApplication1 { internalclassProgram { privatestaticvoidMain(string[]args) { constintn=1000000; varcapacities=newHashSet(); varlist=newList(); for(vari=0;i= 85,000 bytes) LOH does not employ compactionLOH size only growsResult in memory fragmentation leads to OutOfMemory

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Microsoft.IO.RecycableMemoryStream

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- Stop! Youre crazy!!!

- Really?

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Welcome to crazy world!

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FrugalStructListreferencesource

referencesource

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ObjectPoolreferencesourcereferencesource

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Boxesreferencesourcereferencesource

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SmallConcurrentSetOfInts

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UnionCollection

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OneOrMany

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Essentials toolsClr Heap Allocation Analyzer - https://visualstudiogallery.msdn.microsoft.com/f9b47b93-8675-4ae0-9c52-5da8027c4bb8 Heap Allocation Viewer (ReSharper) - https://resharper-plugins.jetbrains.com/packages/ReSharper.HeapView Analyze Performance While Debugging in Visual Studio 2015 - https://msdn.microsoft.com/en-us/magazine/dn973013.aspx LINQPad- https://www.linqpad.net/dotPeek - https://www.jetbrains.com/decompiler/dotMemory - https://www.jetbrains.com/dotmemory/dotMemory Unit - https://www.jetbrains.com/dotmemory/unit/ Process Monitor - https://technet.microsoft.com/en-us/library/bb896645.aspx SourceBrowser - https://github.com/KirillOsenkov/SourceBrowser

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Further readingGarbage Collection Design - https://github.com/dotnet/coreclr/blob/master/Documentation/botr/garbage-collection.md Mpgo - https://msdn.microsoft.com/en-us/library/hh873180(v=vs.110).aspxFundamentals of Garbage Collection - https://msdn.microsoft.com/en-us/library/ee787088(v=vs.110).aspx GC Performance Counters - http://blogs.msdn.com/b/maoni/archive/2004/06/03/148029.aspx Garbage Collector Basics and Performance Hints - https://msdn.microsoft.com/en-us/library/ms973837.aspx A new stackalloc operator for reference types with CoreCLR and Roslyn - https://github.com/xoofx/StackAllocForClassThe Garbage Collection Handbook - http://www.amazon.com/Garbage-Collection-Handbook-Management-Algorithms/dp/1420082795 .NET Type Internals - http://www.codeproject.com/Articles/20481/NET-Type-Internals-From-a-Microsoft-CLR-Perspecti Background and Foreground GC - http://blogs.msdn.com/b/salvapatuel/archive/2009/06/10/background-and-foreground-gc-in-net-4.aspx The 5 stages of solving real-life .NET memory problems - http://www.red-gate.com/products/dotnet-development/ants-memory-profiler/solving-memory-problems/index Under the Hood of .NET Memory Management - https://www.simple-talk.com/redgatebooks/ChrisFarrell/Under_the_Hood_of_NET_Management.pdf

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Questions?

https://twitter.com/Ky7m http://ifesenko.comhttp://ifesenko.com/go/NMH

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